Hydrocarbons, such as oil and gas, are produced from cased wellbores intersecting one or more hydrocarbon reservoirs in a formation. These hydrocarbons flow into the wellbore through perforations in the cased wellbore. Perforations are usually made using a perforating gun that is generally comprised of a steel tube “carrier,” a charge tube riding on the inside of the carrier, and with shaped charges positioned in the charge tube. The gun is lowered into the wellbore on electric wireline, slickline, tubing, coiled tubing, or other conveyance device until it is adjacent to the hydrocarbon producing formation. Thereafter, a surface signal actuates a firing head associated with the perforating gun, which then detonates the shaped charges. Projectiles or jets formed by the explosion of the shaped charges penetrate the casing to thereby allow formation fluids to flow through the perforations and into a production string.
In certain instances, it may be desirable to perforate the formation while the wellbore pressure is less than the formation pressure. This condition is known as an “underbalanced” condition. In an underbalanced condition, the fluid from the formation flows out of a newly formed perforation. This flow can clean the perforation of debris and improve production of resident hydrocarbons. The present disclosure addresses the need for perforating guns that can generate an underbalanced condition during a perforating activity.